Scared and need help!

I am currently 20 weeks pregnant and I had my first ultrasound when I was 10 weeks pregnant. They told me at that ultrasound that I concieved October 29. I slept with my ex boyfriend on October 30th, but then we broke up and I ended up sleeping with someone else on November 9th. I am wondering how accuate this result is and if I can be sure who the father is. My last period was around October 21st and my doctor has been using this information instead of the ultrasound results to calculate how far I am, by estimating that I would have ovulated 15 days after my last period began. I have heard that ultrasounds around the 10th week are usually not off by any more than 3-5 days, so should I worry if it could be off by 9 days?

[JoyRenee]

Only a DNA test can tell you. Those dates are too close together. Conception and due dates are just an estimate and shouldn't be the basis for determining who the father is so definitely get a DNA test once baby is born.

[spade22]

I agree with Joy - the only way to determine who the father is, is with a DNA test since the dates are too close together and ultrasounds can be more than 5 days off.

[Linzola1]

I have to agree with Joy and Spade ypu will have to et a DNA test to prove who the father is! Best of Luck